A Biochemical Study of Curing Processes in Sweet Potatoes.

If sweet potatoes are to be stored for any leilgth of time they must be subjected immediately after digging to a suitable combination of temperature and humidity for effective curing of the roots. The physiology of curing is imperfectly understood because of our limited information of the essential chemical changes in the roots during curing,. Previous studies have been confined chiefly to carbohydrate transformations and respiration. The rate of respiration decreases over that of freshly harvested potatoes (1, 5). Both sucrose and reducing sugars accumulate at the expense of the starch (1, 3, 4). The percentage of moisture changes very little regardless of the amount of shrinkage by loss of water (3, 5). The pH data for expressed juice do not give any significant information on the curing process (5). The present investigation has been concerned with the nitrogen metabolism and pectic transformations in Maryland Golden Sweet Potatoes during curing under different combinations of temperature and humidity and also during subsequent storage under favorable conditions. The keeping qualities of the sweet potatoes cured under the different conditions were recorded in order to determine the relationship of the nitrogen metabolism and pectic changes in the roots during curing to their keeping qualities in storage. The results are also of general physiological interest in relation to the effect of temperature and humidity on nitrogen distribution in fleshy roots. The sweet potatoes for the experimental lots were carefully gathered in the field and placed under experimental conditions the day following their harvest. The lots were cured for 10 or 11 days under the different combinations of temperature and humidity indicated in the tables. All of the lots at the end of the curing period were stored for four months in an electric refrigerator especially equipped to give the desired temperature control. All the lots were stored at 500 to 530 F. and 50 to 60 per cent. relative humidity. Analyses were made at intervals during the curing and storag,e periods.